Vascular abnormalities may occur in a wide variety of anatomical locations and under a wide variety of physiological conditions. As an example, vascular abnormalities occurring in the eye often have significant consequences which may impact the health and well being of a subject. Among the most serious consequences is vision loss.
Vision loss in people over 50 is commonly caused by the localized excessive new growth of blood vessels in the choroid. These concentrations of blood vessels are called Choroidal Neovscular Membranes or “CNVM”.
The choroid is the layer of the eye sandwiched between the retina (the light-registering layer) and the sclera (the tough white outer layer that forms the eyeball). The choroid is a vascular layer rich in blood vessels feeding the retina. A very common disease, Age Related Macular Degeneration (ARMD) is associated with the pathologic growth of new blood vessels in the choroid (Choroidal Neovascular Membranes or CNVM) which penetrate the retina and cause vision loss or blindness.
Most retinal imaging devices are designed to visualize, diagnose, or document the posterior anatomy of the eye. The Carl Zeiss Company of Germany has long dominated this field with a series of products that are designed to maximize the field of view, maximize the image quality, and provide recording capability. This was first done utilizing photography and currently is done utilizing electronic cameras. One type of camera is a fundus camera. The fundus camera owes some of its heritage to work done years earlier on the opthalmoscope. The simple design of this device reveals early attempts at visualizing the posterior anatomy of the eye and describes 3 principle methods for introducing light for viewing the back of the eye. The first method involves a beamsplitter that deviates a source of illumination along a path consisting of an optical line of sight between the subject's eye and the observer's eye. The light enters the eye illuminating the eye and the returning light from the retina passes through the beamsplitter and passes to the observer's eye. If the beamsplitter coating is 50/50 then there is an illumination loss both when the beam path is reflected towards the subject's eye and a loss to the returning light that is directed towards the observer. The second example involves deviating the light source off a front surface mirror mounted nominally at 45 degrees where the mirror is comprised of a hole for light to pass from the subject's eye to the position of the observer. This method was later adopted by Zeiss in the design of the fundus camera. The losses in illumination are related to the area ratios between the reflecting surface and the hole. The third method involves the introduction of source illumination to the axis between subject and observer by means of a front surface mirror segment. Similar to the second method, the loss relationships (ratio of reflecting surface area to viewing path) are first established by the cross sectional areas of the total beam diameter. All three of these methods are nominally called beam combining.
Imaging of the posterior segment of the eye, e.g., the choroid, in cases of age-related macular degeneration has evolved rapidly in the past two decades. Infrared light is now routinely used to visualize features not seen by other methods. Typically the light is provided by a laser. With digitization, the ability to acquire, store and retrieve images has greatly improved. Thus it is now possible to diagnose lesions more effectively. Moreover, methods and devices which provide for imaging and diagnosing abnormalities associated with the choroid, as well as for methods of treating those abnormalities have been described (see, e.g., U.S. Pat. Nos. 5,279,298; 5,394,199, both of which are hereby incorporated by reference in their entirety). These devices however are not without their shortcomings. Among these shortcomings was the inability to provide a well corrected virtual image that was free of aberrations and the difficulties associated with repositioning the lasers during either treatment or visualization.
It would be useful to improve upon known methods by providing a method for introducing multiple illumination and treatment sources (lasers) into the eye and multiple imaging paths exiting the subject's eye towards the observer (recording or imaging device, viewing in the visible and or the near IR). The optical devices should be capable of accommodating a large range of optical wavelengths from deep blue to infrared. Additionally, the device should be able to map the curved posterior of the eye to a flat image plane. The device should also be compact and cost effective while producing high quality images having a sufficient field of view. A need therefore exists for improved devices and methods for imaging abnormal vasculature, e.g., vasculature associated with the eye of a subject.